Chair base



FIG. 1 is an isometric view showing the top side of a chair base having features of the invention;

FIG. 2 is a top view of the chair base illustrated in FIG. 1;

FIG. 3 is a first side view of the chair base illustrated in FIG. 1;

FIG. 4 is a second side view of the chair base illustrated in FIG. 1;

FIG. 5 is a third side view of the chair base illustrated in FIG. 1; and,

FIG. 6 is a bottom view of the chair base illustrated in FIG. 1. 

The ornamental design for a chair base, as shown and described. 